1. Field of the Invention
The present invention relates to a radiator cap applied to a vehicle, and more particularly to a non-negative pressure radiator cap that prevents coolant from flowing back into a reservoir tank when a vacuum valve is opened.
2. Description of the Related Art
Radiators are devices that radiate heat or light to the atmosphere. Since a radiator preferably has a substantially large heat radiation area to increase cooling efficiency, the radiator has a structure in which tanks for storing coolant are installed to both sides of a radiator core formed by welding metal plates (fins), made of a material having a high heat transfer rate, to flat tubes. Additionally, downflow radiators, in which tanks are arranged vertically and coolant flows from top to bottom using the principle of convection, by which hot water flows upward and cold water flows downward, are mainly used. However, crossflow radiators, in which tanks are arranged horizontally and coolant flows laterally, are gradually increased.
Radiator cores are typically formed by welding copper fins to brass tubes, but aluminum radiators, in which both of tubes for passing coolant therethrough and fins coming into contact with air are made of aluminum, which has a reduced specific gravity, are currently being used. Tanks made of resin such as nylon, rather than brass or aluminum, and filled with glass fiber are also being used with the goal of reducing the weight thereof.
Further, a radiator is equipped with a radiator cap for replenishing coolant. A conventional radiator cap is a cap through which coolant communicates with outside air and a pressurized type radiator cap which seals the inside of a radiator is currently used in the related art. In particular, since water boils at 100° C. under atmospheric pressure, and thus, the pressure and boiling point of water are increased in the sealed state, as a result of which the difference between the temperature of water and the temperature of outside air is increased. Therefore, the cooling effect may be increased.
The pressurized type radiator cap is equipped with a pressure valve and a vacuum valve. The pressure valve is opened when the boiling point of coolant increases to a temperature of about 110 to 120° C. and the internal pressure of the radiator increases to a pressure of about 0.9 to 1.0 kgf/cm2, and thus extra coolant is discharged from the radiator. In contrast, the vacuum valve is opened when the temperature of coolant is decreased and the internal pressure of the radiator is a negative pressure, and thus coolant is supplied to the radiator causing the radiator to be filled with coolant.
FIG. 1 is a diagram illustrating a cooling system of a typical fuel cell vehicle according to the related art. A radiator cap CAP in FIG. 1 is disposed at the upper side of a radiator, and coolant is circulated by a water pump PMP. FIG. 2 is a view illustrating a conventional radiator cap CAP, and FIG. 3 is a graph illustrating the operation of FIG. 2 according to the related art. When a vacuum valve 30 is opened or closed, the radiator cap CAP is moved vertically (A) and rotated (B) by a predetermined angle. Accordingly, coolant may flow back into a reservoir tank 700 through the space between the vacuum valve 30 and a sealing member 40. To resolve the above problem, there is a need for a non-negative pressure radiator cap which prevents coolant from flowing back into a reservoir tank when a vacuum valve is opened.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.